BOOK REVIEW : A Complex Story of Real Love and Sex : THE TRESPASSERS, <i> by Robert Roper,</i> Ticknor & Fields, $19.95, 264 pages

Robert Roper is one of the spookiest (and very best) writers in America. His novels vary and change and curl around each other, and just watching this sensuous movement is a pleasure.

His last novel, “Mexico Days,” created a perfect, surreal world full of violence and beauty and lust. This new one, “The Trespassers,” ingenuously passes itself off as a love story cast in the mold of “Lady Chatterly’s Lover,” but it is far more complex than that.

Catherine, a pretty, sturdy, decent woman, has married very well. Her husband, Rick Mansure, is part of one of the great land-holding families in Northern California. Rick has had an intellectually flashy career at Berkeley: He was once a charismatic teaching assistant (T.A.) with a devoted following, then he put together a film class “of an extraordinary, campus-wide popularity.”

After that, he wrote a book, which everybody loved, and then began a regression into what he perhaps was all the time--a greedy Mansure businessman. Rick is all show, flash, dash, will. He loves himself more than life.

Catherine and Rick live on some of the Mansure holdings in a wilderness canyon east of Berkeley and the Bay Area. It is a unique world, beautiful but withering from a decade of drought. Rick withers too.

Shortly after Bob Stein, “an obscure novelist,” comes out to visit them with yet another manuscript, Rick, whose chilly arrogance brooks no competition, suffers a recurrence of childhood polio--or it could be something else altogether, a kind of psychic tantrum about not being the center of attention.

Meanwhile, another man, a “trespasser,” is living on Mansure land. Henry Bascomb lives in a broken-down, book-lined shack, far back in the woods. He’s getting over a bad divorce. Instead of being a gamekeeper, he grows marijuana in unlikely nooks to eke out a perilous living. He has seen Catherine swimming in a Mansure pond and has fallen for her, hook, line and sinker.

D. H. Lawrence had an ax to grind about physical sexuality. A lot more of it would make a lot of people feel better, his line of thinking went. But for Robert Roper it’s sex with love, an incandescent passion, that makes life worth living, passion, and that alone.

Catherine, after her years of dwelling with peevish self-absorbed Rick, is so unhappy that she doesn’t even know she’s unhappy; she’s as drought-stricken as the landscape. But when, inevitably, she and Bascomb begin an affair, it’s not just the sex but the sex with human feeling that slowly brings her back to life.

“You almost killed me,” Bascomb tells her, after they’ve only kissed once and she stays away from him for a month or so. “Did you know? Staying away from me all that time. I almost died, waiting here for you.”

Certainly this is in sharp contrast to what crabby Rick thinks: “Why should a man want to get that close to a woman? Why really should he want to study you, ponder you for his whole life? . . . Where is it written that we should worship at your feet--that we should want to probe and mull you over endlessly, as if you were the greatest of mysteries?”

As Catherine and Bascomb move closer and closer together, the author underscores his thesis that sex without love is the ultimate snore, that lack of feeling is equivalent to and underscores the drought in which they live.

Bascomb’s ex-wife takes Catherine out for a beer and regales her of tales of her own sexual exploits, implying that Henry is a wimp for wanting to attach meaning to every little spasm. The dreaded Rick “recovers” enough to bring a money-hungry slut into Catherine’s own bed. Then he turns Catherine’s own “best friend” against her. Rick’s great-aunt frets: If Catherine leaves Rick, then all the Mansure land will go to Rick and Rick alone, and she hates that guy.

But the larger world deals in money, power, prestige, insults, meanness, inheritance and so on and so forth. Lovers deal in something else entirely--the quality of being alive, instead of going through the motions.

There are other shadings to this tale. Roper inserts himself in the narrative, as the author of “The Poacher,” for instance, asking himself and the reader to test the ethical limits of putting people you know into your stories. But the clear and beautiful message here is: If you’re lucky enough to find real love, all the rant and rave of the whole rest of the world doesn’t mean a thing.